The present invention relates to a golf ball material for use in at least one of the layers making up a golf ball, such as the core or cover. More specifically, the invention relates to a golf ball material composed of an ionomer composition, the hardness of which has been increased with a phenolic resin component. The present invention relates further to a golf ball having, as an essential part thereof, a molding made of such a golf ball material, and relates still further to a method for preparing such a golf ball material.
Various ionomers (typical products include those commercially sold under the trade names “Surlyn,” produced by E.I. DuPont de Nemours & Company; “Iotek,” produced by Exxon Chemical; and “Primacor,” produced by Dow Chemical) are used as constituents in many golf balls. Tradition balata rubber is flexible and has an excellent resilience, but lacks durability. Compared with balata rubber, ionomers have a poor resilience but an excellent durability, which is why they are still in use today.
Approaches commonly taken to increase the resilience of ionomers employed in golf balls include using an ionomer base polymer having a high acid content and subjecting it to a high degree of neutralization with metal cations, including a higher fatty acid in the ionomer base polymer and subjecting the base polymer to a high degree of neutralization, combining different metal cationic species within the ionomer, and blending into the ionomer a thermoplastic material having a high resilience. Numerous patent applications have been filed relating to each of these approaches.
Examples include Patent Document 1: U.S. Pat. No. 6,100,340, Patent Document 2: U.S. Pat. No. 6,117,026, Patent Document 3: U.S. Pat. No. 6,277,921, Patent Document 4: U.S. Pat. No. 6,433,094, Patent Document 5: U.S. Pat. No. 6,494,792 and Patent Document 6: U.S. Pat. No. 6,852,043, all of which describe golf balls that use ionomers having a high acid content and a high degree of neutralization; Patent Document 7: U.S. Pat. No. 6,100,321, Patent Document 8: U.S. Pat. No. 6,653,382, Patent Document 9: U.S. Pat. No. 6,329,458, Patent Document 10: U.S. Pat. No. 6,962,951 and Patent Document 11: U.S. Pat. No. 7,402,114, all of which describe golf balls that use ionomer compositions obtained by including a higher fatty acid in an ionomer base polymer and subjecting the base polymer to a high degree of neutralization; Patent Document 12: U.S. Pat. No. 4,984,804, Patent Document 13: U.S. Pat. No. 5,197,740, Patent Document 14: U.S. Pat. No. 5,492,972, Patent Document 15: U.S. Pat. No. 5,837,775 and Patent Document 16: U.S. Pat. No. 6,494,792, all of which describe golf balls that use ionomer compositions obtained by combining different metal cationic species within the ionomer; and Patent Document 17: U.S. Pat. No. 5,625,003, Patent Document 18: U.S. Pat. No. 5,631,324, Patent Document 19: U.S. Pat. No. 5,824,746, Patent Document 20: U.S. Pat. No. 6,359,065 and Patent Document 21: U.S. Pat. No. 6,905,425, all of which describe golf balls that use an ionomer composition in which has been blended a thermoplastic material having a high resilience.
Of the above, golf balls which use an ionomer having a high degree of neutralization generally are endowed with a high resilience and a high hardness, but have a poor durability. Moreover, ionomer compositions which use a base polymer having a high acid content are expensive. Golf balls made using ionomers which contain a higher fatty acid and have a high degree of neutralization also tend to exhibit a poor durability.
Lately, there continues to exist a desire, with regard to golf balls made using ionomer components, to reduce the spin of the ball at high swing velocities (head speeds) and thus increase by a corresponding amount the distance traveled by the ball. There is also a desire, concerning golf balls made using relatively inexpensive, moderate acid-content ionomers instead of the above costly, high acid-content ionomer components, to increase the hardness of the ball and reduce the spin, thereby extending the distance traveled by the ball.
Patent Document 1: U.S. Pat. No. 6,100,340
Patent Document 2: U.S. Pat. No. 6,117,026
Patent Document 3: U.S. Pat. No. 6,494,792
Patent Document 4: U.S. Pat. No. 6,852,043
Patent Document 5: U.S. Pat. No. 6,494,792
Patent Document 6: U.S. Pat. No. 6,852,043
Patent Document 7: U.S. Pat. No. 6,100,321
Patent Document 8: U.S. Pat. No. 6,653,382
Patent Document 9: U.S. Pat. No. 6,329,458
Patent Document 10: U.S. Pat. No. 6,962,951
Patent Document 11: U.S. Pat. No. 7,402,114
Patent Document 12: U.S. Pat. No. 4,984,804
Patent Document 13: U.S. Pat. No. 5,197,740
Patent Document 14: U.S. Pat. No. 5,492,972
Patent Document 15: U.S. Pat. No. 5,837,775
Patent Document 16: U.S. Pat. No. 6,494,792
Patent Document 17: U.S. Pat. No. 5,625,003
Patent Document 18: U.S. Pat. No. 5,631,324
Patent Document 19: U.S. Pat. No. 5,824,746
Patent Document 20: U.S. Pat. No. 6,359,065
Patent Document 21: U.S. Pat. No. 6,905,425